title: Potentiated adrenomedullin-induced vasorelaxation during hypoxia in organ cultured porcine coronary arteries.
abstract: This study describes the effect of variable oxygen supply on relaxing responses induced by α-calcitonin gene-related peptide (CGRP) and adrenomedullin (AM) on isolated pig coronary arteries in vitro. Organ culture during normoxia (21% of O₂) and hypoxia (5% of O₂) induced a significant leftward shift of the AM concentration-response curves compared with fresh vessels altering the pEC₅₀ values from 6.9 ± 0.04 to 8.0 ± 0.04, whereas the potency (pEC₅₀) of αCGRP was attenuated from 8.8 ± 0.04 to 7.6 ± 0.04. AM₂₂₋₅₂ exerted significant antagonistic effect on AM-induced vasorelaxation in hypoxic and normoxic conditions (apparent pK(B) = 6.8-7.2), whereas no antagonistic effect was observed in fresh and hyperoxic (95%) organ cultured vessels. The antagonistic effect exerted by αCGRP₈₋₃₇ (10⁻⁶·⁵-10⁻⁵·⁵ M) on αCGRP-induced vasodilatation in fresh vessels (derived from Schild plot pA₂ = 7.4 ± 0.1) was unaltered during organ culture. The antagonistic effect exerted by αCGRP₈₋₃₇ (10⁻⁶ M) on AM-induced vasorelaxation in fresh vessels (apparent pK(B) = 7.4 ± 0.1) was absent during hypoxic organ culture. The receptor activity-modifying proteins 1 (RAMP1)/calcitonin-like receptor (CLR) messenger RNA ratio was reduced and RAMP2/CLR messenger RNA ratio was increased during hypoxic and normoxic organ culture compared with fresh vessels. Hypoxic organ culture for 24-72 hours potentiated the AM-induced vasorelaxation through an AM₂₂₋₅₂-sensitive receptor but attenuated the vasorelaxant effect of CGRP through the CGRP receptors. This could possibly be explained by relatively decreased levels of RAMP1, thus favoring RAMP2 + CLR complex (=AM receptor) formation during hypoxic organ culture.
authors.affiliation: Departments of *Clinical Experimental Research; and †Clinical Physiology and Nuclear Medicine, University Hospital of Glostrup, Glostrup, Denmark; ‡Department of Clinical Physiology, Nuclear Medicine, and PET, Rigshospitalet, Copenhagen University Hospital, København Ø, Denmark; §Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark; and ¶Department of Nuclear Medicine, Odense University Hospital, Odense, Denmark.
authors.forename: Philip
authors.initials: P
authors.lastname: Hasbak
authors.forename: Majid
authors.initials: M
authors.lastname: Sheykhzade
authors.forename: Søren
authors.initials: S
authors.lastname: Schifter
authors.forename: Lars
authors.initials: L
authors.lastname: Edvinsson
mesh_terms: D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D053607:Adrenomedullin / Q000494:pharmacology*; D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism; D058286:Calcitonin Receptor-Like Protein / Q000096:biosynthesis; D003331:Coronary Vessels / Q000187:drug effects*; D000860:Hypoxia / Q000503:physiopathology*; D009119:Muscle Contraction / Q000187:drug effects; D009206:Myocardium / Q000378:metabolism; D009924:Organ Culture Techniques; D010446:Peptide Fragments / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D058261:Receptor Activity-Modifying Proteins / Q000378:metabolism; D013552:Swine; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology*
chemical_list: D058286:Calcitonin Receptor-Like Protein; D010446:Peptide Fragments; D012333:RNA, Messenger; D058261:Receptor Activity-Modifying Proteins; D014665:Vasodilator Agents; C058636:calcitonin gene-related peptide (8-37); D053607:Adrenomedullin; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D015740:Calcitonin Gene-Related Peptide